1. Field of the Invention
The present invention relates to power feedback power factor correction high frequency inverters, and more particularly to the power feedback power factor correction high frequency inverter used for a lamp ballast.
2. The Prior Arts
Electronic lamp ballasts currently available on market have a circuit as shown in FIG. 1, which comprises an AC (alternate current) filter circuit 10, a bridge rectifier circuit 11, a DC (direct current) rectifier circuit 12 and a DC/AC conversion circuit 13. The electronic lamp ballast drives a lamp tube 14 to start irradiating. However, the DC rectifier circuit 12 of the known electronic ballast uses only a single capacitor 20 to form the filter circuit. Although it has the advantages of low cost, simple circuit, and high load variation resistance, yet this type of filter circuit has a shorter period of charging current which occurs only when the voltage at the power source side is higher than the voltage drop across the capacitor at its DC output side. Therefore, the known circuit produces a large ripple current and, consequently, leads to low efficiency. As such, the power factor of the known ballast is merely between 0.5 and 0.6 as shown in FIG. 2, which shows, for the known device, the input ripple current is large and the power factor is low. This phenomenon apparently leads to the result of increasing power consumption and the waste of power.
Due to the shortcomings and restrictions imposed on the conventional electronic lamp ballast, it is desired to provide a ballast having a power feedback power factor correction high frequency inverter to overcome the shortcomings and restrictions.